For decades, millions of fish have been diverted from pumping facilities at state and federal water projects in the Sacramento-San Joaquin Delta. Fish -- including endangered species like the Delta smelt-- are put in holding tanks then trucked to other parts of the Delta and released. From there, little is known about their fate. But most scientists agree it’s not good. As Amy Quinton reports from Sacramento, predator fish often wait for what amounts to a daily feeding.

"The predators would really sit within a couple of feet from that pipe waiting for fish to come out." - Javier Miranda

Imagine you’re an endangered Delta smelt. You’re not quite three inches long; you can’t swim very well so you mainly ride on the current. That current could take you to the not-so quiet Skinner Fish Facilities in Tracy.

From there you flow through pipes and into an 1,100 gallon holding tank. Jim Odom with the California Department of Water Resources runs those facilities.

“That’s our whole intent is to salvage all those small fish before they get into the system so they get lost and never can return,” says Odom.

The system is the state water project, where water from the Delta is pumped to Central and Southern California. After being counted, a mechanical bucket loads you, the lowly smelt and all kinds of other fish, into a tanker truck. Some of those other fish may be hungry.

“The longer we keep them in captivity the more chance they have of perishing or being eaten up by some of the other predators that we’re salvaging. We salvage everything that comes through the system gets loaded up here and hauled back,” says Odom.

A truck dumps fish into the Delta at the DWR release site

Credit Amy Quinton / Capital Public Radio

Your tanker truck then travels to Sherman Island and backs up to one of two release sites. A big pipe shoots you and all those other fish 50 feet out into the water. And, if you survive that process, which isn’t likely, death may await you at the end of the pipe.

“The predators would really sit within a couple of feet from that pipe waiting for fish to come out,” says Javier Miranda, an environmental scientist with the Department of Water Resources. A few years ago as part of a predation study, he lowered a sonar camera in the murky Delta waters to find out exactly what was going on.

“We thought there might be kind of a dinner bell effect where when they heard the truck drive up they’d all come up to the site,” says Miranda.

Like Pavlov’s fish, salivating.

“As it turned out, when the predators were there they were always there, they were waiting,” says Miranda.

Large-mouth bass, striped bass, Sacramento pikeminnow and other predators await most of the salvaged fish.

“We could see fish kind of coming out of the pipe and on a good day you would see them kind of swim off and other days when there was predators there you would see them get picked off,” says Miranda.

The study also showed the predators were seasonal, showing up in the summer months when tens of thousands of fish would be released on any given day. But if you’re a smelt, there is some good news.

“One of the good things we saw from our study was that during the months where we had endangered species like Delta smelt, salmon, we didn’t see a lot of predators at those sites,” says Miranda.

It’s still not a good fate for most salvaged fish. Brent Bridges is a fish biologist at the Tracy fish facilities, part of the Bureau of Reclamation’s Central Valley Project. They have the same problem at their release sites. Bridges says they’re now trying to trick the predators by turning on and off the pumps at the release site.

A holding tank where fish are held before a mechanical bucket removes them to put them in the tanker truck.

Credit Amy Quinton / Capital Public Radio

“The idea is that we want to prevent the fish, the predators, from realizing they’re going to be fed, because we just don’t want them to learn that when they hear the pump running they’re going to get fed,” says Bridges.

Bridges says biologists don’t know whether the predation at the release sites is actually affecting fish populations in the Delta. But he says both the state and the federal water projects are building more release sites, so they can use a different site every day of the week. Javier Miranda says studies show in the Delta predation is high and survival is low.

“So it’s kind of a trade off of predation in the river or predation in our salvage process, unfortunately the science is just kind of getting caught up right now in terms of what’s better river versus salvage but you could ask a lot of people and they’d say it’s better to have those fish go through the salvage process,” says Miranda.

He says, for salmon, the salvage process is a short cut through the Delta and out to the ocean. But if you’re a fragile smelt, the forces are against you, even if you make it to that holding tank.